Title : Unravelling the One Health Dynamics of Antimicrobial Resistance in Escherichia coli Across Dairy Farms in Malaysia
Abstract:
Antimicrobial resistance (AMR) is a growing One Health concern driven by the interconnected transmission of resistant bacteria among humans, animals, and the environment. Dairy farms represent important reservoirs where antimicrobial-resistant bacteria and resistance determinants can emerge, persist, and disseminate. Escherichia coli is widely used as an indicator organism for AMR surveillance due to its widespread presence in ecosystems and its ability to acquire resistance-associated genetic elements. This study aimed to investigate the AMR profiles and genomic characteristics of E. coli isolated from dairy-associated sources, including humans (hand and throat swabs), animals (cow dung), the environment (soil and effluent), and food products (milk). Samples were collected from eight dairy farms in Selangor, Malaysia, between 2022 and 2023. The samples underwent serial dilution and spread plating, followed by bacterial isolation and Gram staining. Bacterial identification and antimicrobial susceptibility testing were performed using the Vitek 2 system. Selected isolates representing diverse resistance profiles were further analysed using whole-genome sequencing on the Illumina platform. A total of 412 E. coli isolates were recovered and identified. Phenotypic analysis showed diverse resistance patterns, with multidrug-resistant isolates detected across multiple sources. The highest level of resistance was observed against ampicillin (18.7%), followed by trimethoprim-sulfamethoxazole (8.9%). Genomic analysis demonstrated genetic diversity among the isolates, including multiple sequence types, antimicrobial resistance genes, and plasmid replicons associated with resistance. Phylogenetic analysis revealed genetic similarities among E. coli strains from different sample sources, suggesting dissemination of resistant bacteria within the dairy ecosystem. This study underscores the interconnected nature of AMR across human, animal, environmental, and food interfaces within the dairy ecosystem. The findings highlight the importance of integrating phenotypic and genomic approaches to enhance One Health AMR surveillance, safeguard environmental health, and support effective control strategies.
